Low gauge films and film/nonwoven laminates

ABSTRACT

Disclosed herein is a low gauge, multilayer film which may be laminated to other materials such as, for example, fibrous nonwoven webs. The multilayer film may include one or more skin layers which in certain configurations comprise no more than about 15 percent of the overall thickness and in other configurations no more than about 10 percent of the overall thickness of the multilayer film. Such films and laminates have a wide variety of uses including, but not limited to, personal care absorbent products, articles of clothing and health care related items such as surgical drapes and gowns.

This application is a continuation of application Ser. No. 08/724,435filed in the U.S. Patent and Trademark Office on Oct. 1, 1996, and nowU.S. Pat. No. 6,075,179, which is a file wrapper continuation ofapplication Ser. No. 08/359,986 filed in the U.S. Patent and TrademarkOffice on Dec. 20, 1994, now abandoned, all entitled Low Gauge Films andFilm/Nonwoven Laminates. The entirety of the aforesaid applications arehereby incorporated by reference.

FIELD OF INVENTION

The present invention is directed to low gauge, multi-layer films withskin layers that are extremely thin. In addition, the present inventionis directed to such films laminated to other materials such as, forexample, fibrous nonwoven webs.

BACKGROUND OF THE INVENTION

The present invention is directed to extremely thin multi-layer filmsand their use with laminates. Such materials have a wide variety ofuses, especially in the areas of limited use and disposable items.

Many products today require highly engineered components and yet, at thesame time, these products are required to be limited use or disposableitems. By limited use or disposable, it is meant that the product and/orcomponent is used only a small number of times or possibly only oncebefore being discarded. Examples of such products include, but are notlimited to, surgical and health care related products such as surgicaldrapes and gowns, disposable work wear such as coveralls and lab coatsand a personal care absorbent products such as diapers, training pants,incontinence garments, sanitary napkins, bandages, wipes and the like.All of these products can and do utilize as components, films andfibrous nonwoven webs. While both materials are often usedinterchangeably, films tend to have greater barrier properties,especially to liquids while fibrous nonwovens webs have, among otherthings, better tactile, comfort and aesthetic properties. When thesematerials are used in limited use and/or disposable products, theimpetus for maximizing engineered properties while reducing cost isextremely high. To this end, it is often desirable to use either a filmor a nonwoven to achieve the desired results because the combinationoften becomes more expensive. In the area of films, there have beenprevious attempts to make multi-layer films with reduced thicknesses.See, for example, U.S. Pat. No. 5,261,899 to Vischer wherein a threelayer film is made with a central layer that comprises from about 30 to70% of the total thickness of the multi-layer film. One advantage informing multi-layer films is that specific properties can be designedinto the film, and, by making the films multi-layer the more costlyingredients can be relegated to the outer layers where they are mostlikely to be needed.

It is an object of the present invention to provide a multilayer filmwhich can be engineered to provide specific properties while providingsuch properties in a very thin gauge. Another object of the presentinvention is to combine such low gauge films with other support layerssuch as layers of fibrous nonwoven webs to increase strength and provideaesthetic properties. The means by which such objectives are achievedcan be more fully comprehended by a review of the followingspecification, drawings and claims.

SUMMARY OF THE INVENTION

The present invention is directed to multilayer films and multilayerfilm/nonwoven laminates. The films are made by conventional film formingtechniques such as cast and blown coextrusion film forming processes.The films are created with a core layer made from an extrudablethermoplastic polymer with the core layer defining a first exteriorsurface and a second exterior surface. In the most basic configuration,a first skin layer is attached, usually simultaneously due to thecoextrusion process, to the first exterior surface of the core layer toform a multilayer film. The multilayer film defines an overall thicknesswith the first skin layer defining a first skin thickness whichcomprises less than about 10 percent of the overall thickness of themultilayer film. This is due to the stretching of the extruded film tosuch a degree so as to thin the multilayer film to within the dimensionsdefined herein. As a result, the thickness of the first skin layer willnot exceed about 2 micrometers. Given the extremely thin nature of themultilayer film, it may be desirable to laminate the multilayer film toanother material such as a support layer. Suitable support layersinclude, but are not limited to, such materials as other films, fibrousnonwoven webs, woven materials, scrims, netting and combinations of theforegoing.

In other embodiments of the present invention, the core layer may have afirst skin layer attached to the first exterior surface of the corelayer and a second skin layer attached to the second exterior surface ofthe core layer. In such situations, the first skin and the second skinlayer should have a combined thickness which does not exceed about 15percent of the overall thickness and more desirably where neither thefirst skin thickness nor the second skin thickness exceeds more thanabout 7.5 percent of the overall thickness of the multilayer film. Ifdesired, one or more of the layers may contain other additives such as,for example, a particulate filler. Most typically, such fillers will beprimarily utilized in the core layer in, for example, a weight percentof at least about 60 percent, based upon the total weight of thatparticular layer.

It is also possible to make multilayer films which are breathable eitherthrough the use of specialized polymers which permit diffusion of gasesthrough the layers and/or through the use of particulate fillers.Normally, to make such films breathable, they are stretched and/orcrushed between compression rollers so as create voids in and around theparticles to permit the transmission of water vapor and other gases.Typically such breathable multilayer films will have water vaportransmission rates of at least 300 grams per square meter per 24 hours.

Such films and laminates have a wide variety of uses including, but notlimited to, applications in personal care absorbent articles includingdiapers, training pants, sanitary napkins, incontinence devices,bandages and the like. These same films and laminates also may be usedin items such as surgical drapes and gowns as well as various articlesof clothing either as the entire article or simply as a componentthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional side view of a multilayer film according tothe present invention. The right side of the film has been split apartto facilitate its description.

FIG. 2 is a cross-sectional side view of a multilayer film/nonwovenlaminate according to the present invention.

FIG. 3 is a schematic side view of a process for forming a multilayerfilm according to the present invention and a multilayer film/nonwovenlaminate according to the present invention.

FIG. 4 is a partially cut away top plan view of an exemplary personalcare absorbent article, in this case a diaper, which may utilize amultilayer film and multilayer film/nonwoven laminate according to thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to multilayer films, that is, filmshaving two or more layers as well as such films laminated to supportlayers such as, for example, fibrous nonwoven webs. Referring to FIG. 1,there is shown, not to scale, a multilayer film 10 which, for purposesof illustration, has been split apart at the right side of the drawing.The multilayer film 10 includes a core layer 12 made from an extrudablethermoplastic polymer such as a polyolefin or a blend of polyolefins.The core layer 12 has a first exterior surface 14 and a second exteriorsurface 16. The core layer also has a core thickness 22. Attached to thefirst exterior surface 14 of the core layer 12 is a first skin layer 18which has a first skin thickness 24. Attached to the second exteriorsurface 16 of the core layer 12 is an optional second skin layer 20which has a second skin thickness 26. In addition, the multilayer film10 has an overall thickness 28. Such multilayer films 10 can be formedby a wide variety of processes well known to those of ordinary skill inthe film forming industry. Two particularly advantageous processes arecast film coextrusion processes and blown film coextrusion processes. Insuch processes, the two or three layers are formed simultaneously andexit the extruder in a multilayer form. Due to the extremely thin natureof the multilayer films according to the present invention suchprocesses will most likely prove to be the most advantageous though italso may be possible to form multilayer films using separate extrusionprocesses. For more information regarding such processes, see, forexample, U.S. Pat. Nos. 4,522,203; 4,494,629 and 4,734,324 which areincorporated herein by reference in their entirety.

An important feature of the present invention is the ability to utilizea more generic core layer 12 in conjunction with a much thinner and morespecially designed skin layer such as the first skin layer 18 or acombination of two or more skin layers attached to either or both sidesof the core layer 12. Thus, it is possible to form multilayer films 10with many layers of material. The core layer 12 as with the first skinlayer 18 and optional second skin layer 20 may be formed from anypolymers which are capable of being utilized in multilayer filmconstructions including, but not limited to, polyolefins includinghomopolymers, copolymers, and blends. To further reduce the cost of thecore layer 12 one or more types of fillers may be added to the corelayer polymer extrusion blend. Both organic and inorganic fillers may beused. The fillers should be selected so as to not chemically interferewith or adversely affect the extruded film. These fillers can be used toreduce the amount of polymer being used for the core layer 12 and/or toimpart particular properties such as breathability and/or odorreduction. Examples of fillers can include, but are not limited to,calcium carbonate (CaCO₃), various kinds of clay, silica (SiO₂),alumina, barium sulfate, sodium carbonate, talc, magnesium sulfate,titanium dioxide, zeolites, aluminum sulfate, cellulose-type powders,diatomaceous earth, magnesium sulfate, magnesium carbonate, bariumcarbonate, kaolin, mica, carbon, calcium oxide, magnesium oxide,aluminum hydroxide, pulp powder, wood powder, cellulose derivatives,polymer particles, chitin and chitin derivatives.

The amount of filler that can be used resides within the discretion ofthe end-user, however, additions of from 0 to 80% by weight based uponthe total weight of the core layer 12 are possible. Generally thefillers will be in particulate form and usually will have somewhat of aspherical shape with average particle sizes in the range of about 0.1 toabout 7 microns. Furthermore, if sufficient filler is used incombination with sufficient stretching of the multilayer film 10, thenvoids can be created around the particles contained within the corelayer 12 thereby making the core layer breathable. High loadings, inexcess of about 60 percent by weight of the core layer 12 when combinedwith stretching provides films which are breathable. Such breathablefilms will generally have Water Vapor Transmission Rates (WVTR) inexcess of 300 grams per square meter per 24 hours.

The skin layers 18 and 20 will typically include extrudablethermoplastic polymers and/or additives which provide specializedproperties to the multilayer film 10. Thus, the first skin layer 18and/or the second skin layer 20 may be made from polymers which givesuch properties as antimicrobial activity, water vapor transmission,adhesion and/or antiblocking properties. Thus, the particular polymer orpolymers chosen for the skin layer 18 and 20 will depend upon theparticular attributes desired. Examples of possible polymers that may beused alone or in combination include homopolymers, copolymers and blendsof polyolefins as well as ethylene vinyl acetate (EVA), ethylene ethylacrylate (EEA), ethylene acrylic acid (EAA), ethylene methyl acrylate(EMA), ethylene butyl acrylate (EBA), polyester (PET), nylon (PA),ethylene vinyl alcohol (EVOH), polystyrene (PS), polyurethane (PU) andolefinic thermoplastic elastomers which are multistep reactor productswherein an amorphous ethylene propylene random copolymer is molecularlydispersed in a predominately semicrystalline high polypropylenemonomer/low ethylene monomer continuous matrix.

Oftentimes it may be desirable to laminate the multilayer film 10 to oneor more substrates or support layers 30 such as is shown in FIG. 2. Thecore layer may not have sufficient adhesive or attachment properties soas to make it bondable to the support layer 30. As a result, the firstskin layer 18 may be made from a polymer or polymers which exhibithigher adhesive properties and/or a lower tack point than the core layer12.

A desired result with respect to the material of the present inventionis to achieve a very low overall film thickness and more importantly,skin layers which are only a small percentage of the overall thicknessof the multilayer film 10. As demonstrated by the examples below, basedupon the overall thickness 28 of the multilayer film 10, in two layerconstructions the first skin thickness 24 of the first skin layer 18should not exceed more than 10 percent of the overall thickness 28. Inthree layer film constructions the combined thickness of the first skinlayer 18 and second skin layer 20 should not exceed 15 percent of theoverall thickness and generally, the first skin layer 18 should notexceed more than 7.5 percent of the overall skin thickness 28. The sameis also true with respect to the second skin layer 20. As a result, thecore thickness 22 comprises at least 85 percent of the overall thickness28 and the first skin layer 18 and second skin layer 20 each generallywill comprise no more than 7.5 percent of the overall thickness 28.Generally, it has been possible to create thinned films with overallthicknesses 28 of 30 microns or less and in certain applications withskin layers that do not exceed two microns. This is made possible byfirst forming a multilayer film 10 and then stretching or orienting thefilm in the machine direction, as explained in greater detail below,such that the resultant multilayer film 10 has increased strengthproperties in the machine direction, i.e., the direction which isparallel to the direction of the film as it is taken off the filmextrusion equipment.

The resultant film can, if desired, be laminated to one or more supportlayers 30 as are shown in FIG. 2. The support layers 30 as shown in FIG.2 are fibrous nonwoven webs. The manufacture of such fibrous nonwovenwebs is well known to those of ordinary skill in the art of nonwovenmanufacturing. Such fibrous nonwoven webs can add additional propertiesto the multilayer film 10 such as, a more soft, cloth-like feel. This isparticularly advantageous when the multilayer film 10 is being used as abarrier layer to liquids in such applications as outer covers forpersonal care absorbent articles and as barrier materials for hospital,surgical, and clean room applications such as, for example, surgicaldrapes, gowns and other forms of apparel. Attachment of the supportlayers 30 to the first skin layer 18 and second skin layer 20 may be bythe use of a separate adhesive such as hot-melt and solvent basedadhesives or through the use of heat and/or pressure as with heatedbonding rolls. As a result, it may be desirable to design either or boththe first skin layer 18 and the second skin layer 20 so as to haveinherent adhesive properties to facilitate the lamination process.

A particularly advantageous support layer is a fibrous nonwoven web.Such webs may be formed from a number of processes including, but notlimited to, spunbonding, meltblowing and bonded carded web processes.Meltblown fibers are formed by extruding molten thermoplastic materialthrough a plurality of fine, usually circular, die capillaries as moltenthreads or filaments into a high velocity usually heated gas stream suchas air, which attenuates the filaments of molten thermoplastic materialto reduce their diameters. Thereafter, the meltblown fibers are carriedby the high velocity usually heated gas stream and are deposited on acollecting surface to form a web of randomly dispersed meltblown fibers.The meltblown process is well-known and is described in various patentsand publications, including NRL Report 4364, “Manufacture of Super-FineOrganic Fibers” by B. A. Wendt, E. L. Boone and C. D. Fluharty; NRLReport 5265, “An Improved Device For The Formation of Super-FineThermoplastic Fibers” by K. D. Lawrence, R. T. Lukas, J. A. Young; U.S.Pat. No. 3,676,242, issued Jul. 11, 1972, to Prentice; and U.S. Pat. No.3,849,241, issued Nov. 19, 1974, to Buntin, et al. The foregoingreferences are incorporated herein by reference in their entirety.

Spunbond fibers are formed by extruding a molten thermoplastic materialas filaments from a plurality of fine, usually circular, capillaries ina spinnerette with the diameter of the extruded filaments then beingrapidly reduced, for example, by non-eductive or eductive fluid-drawingor other well-known spunbonding mechanisms. The production of spunbondnonwoven webs is illustrated in patents such as Appel et al., U.S. Pat.No. 4,340,563; Matsuki, et al, U.S. Pat. No. 3,802,817; Dorschner etal., U.S. Pat. No. 3,692,618; Kinney, U.S. Pat. Nos. 3,338,992 and3,341,394; Levy, U.S. Pat. No. 3,276,944; Peterson, U.S. Pat. No.3,502,538; Hartman, U.S. Pat. No. 3,502,763; Dobo et al., U.S. Pat. No.3,542,615; and Harmon, Canadian Patent Number 803,714. All of theforegoing references are incorporated herein by reference in theirentirety.

Multilayer support layers 30 also may be used. Examples of suchmaterials can include, for example, spunbond/meltblown laminates andspunbond/meltblown/spunbond laminates such as are taught in Brock etal., U.S. Pat. No. 4,041,203 which is incorporated herein by referencein its entirety.

Bonded carded webs are made from staple fibers which are usuallypurchased in bales. The bales are placed in a picker which separates thefibers. Next the fibers are sent through a combing or carding unit whichfurther breaks apart and aligns the staple fibers in the machinedirection so as to form a machine direction-oriented fibrous nonwovenweb. Once the web has been formed, it is then bonded by one or more ofseveral bonding methods. One bonding method is powder bonding wherein apowdered adhesive is distributed throughout the web and then activated,usually by heating the web and adhesive with hot air. Another bondingmethod is pattern bonding wherein heated calender rolls or ultrasonicbonding equipment is used to bond the fibers together, usually in alocalized bond pattern though the web can be bonded across its entiresurface if so desired. When using bicomponent staple fibers, through-airbonding equipment is, for many applications, especially advantageous.

A process for forming the multilayer film 10 is shown in FIG. 3 of thedrawings. Referring to the figure, the multilayer film 10 is formed froma coextrusion film apparatus 40 such as a cast or blown unit as waspreviously described above. Typically the apparatus 40 will include twoor more polymer extruders 41. The multilayer film 10 is extruded into apair of nip or chill rollers 42 one of which may be patterned so as toimpart an embossed pattern to the newly formed film 10. This isparticularly advantageous to reduce the gloss of the film and give it amatte finish. Using a three layer film construction such as is shown inFIG. 1, typically the multilayer film 10, as initially formed, will havean overall thickness 28 of approximately 40 microns or greater with thefirst skin layer 18 and the second skin layer 20 each having initialthicknesses of 3 microns or greater which collectively is approximately15% of the overall initial thickness.

From the coextrusion film apparatus 40 the film 10 is directed to a filmstretching unit 44 such as a machine direction orienter which is acommercially available device from vendors such as the Marshall andWilliams Company of Providence, R.I. Such an apparatus 44 has aplurality of stretching rollers 46 which progressively stretch and thinthe multilayer film 10 in the machine direction of the film which is thedirection of travel of the film 10 through the process as shown in FIG.3. After exiting the film stretching unit 44 the film 10 should have amaximum thickness of approximately 30 microns and each of the skinlayers should have a maximum thickness of no more than about 2 micronswhich in turn is collectively less than about 15 percent of the overallfilm and more desirably less than 10 percent of the overall filmthickness.

If desired, the multilayer film 10 may be attached to one or moresupport layers 30 to form a multilayer film/nonwoven laminate 32.Referring again to FIG. 3, a conventional fibrous nonwoven web formingapparatus 48, such as a pair of spunbond machines, is used to form thesupport layer 30. The long, essentially continuous fibers 50 aredeposited onto a forming wire 52 as an unbonded web 54 and the unbondedweb 54 is then sent through a pair of bonding rolls 56 to bond thefibers together and increase the tear strength of the resultant websupport layer 30. One or both of the rolls are often heated to aid inbonding. Typically, one of the rolls 56 is also patterned so as toimpart a discrete bond pattern with a prescribed bond surface area tothe web 30. The other roll is usually a smooth anvil roll but this rollalso may be patterned if so desired. Once the multilayer film 10 hasbeen sufficiently thinned and oriented and the support layer 30 has beenformed, the two layers are brought together and laminated to one anotherusing a pair laminating rolls or other means 58. As with the bondingrolls 56, the laminating rolls 58 may be heated. Also, at least one ofthe rolls may be patterned to create a discrete bond pattern with aprescribed bond surface area for the resultant laminate 32. Generally,the maximum bond point surface area for a given area of surface on oneside of the laminate 32 will not exceed about 50 percent of the totalsurface area. There are a number of discrete bond patterns which may beused. See, for example, Brock et al., U.S. Pat. No. 4,041,203 which isincorporated herein by reference in its entirety. Once the laminate 32exits the laminating rolls 58, it may be wound up into a roll 60 forsubsequent processing. Alternatively, the laminate 32 may continuein-line for further processing or conversion.

The process shown in FIG. 3 also may be used to create a three layerlaminate 32 such as is shown in FIG. 2 of the drawings. The onlymodification to the previously described process is to feed a supply 62of a second fibrous nonwoven web support layer 30 into the laminatingrolls 58 on a side of the multilayer film 10 opposite that of the otherfibrous nonwoven web support layer 30. As shown in FIG. 3, the supply ofsupport layer 30 is in the form of a preformed roll 62. Alternatively,as with the other layers, the support layer 30 may be formed directlyin-line. In either event, the second support layer 30 is fed into thelaminating rolls 58 and is laminated to the multilayer film 10 in thesame fashion as the other support layer 30.

As has been stated previously, the multilayer film 10 and the laminate32 may be used in a wide variety of applications not the least of whichincludes personal care absorbent articles such as diapers, trainingpants, incontinence devices and feminine hygiene products such assanitary napkins. An exemplary article 80, in this case a diaper, isshown in FIG. 4 of the drawings. Referring to FIG. 4, most such personalcare absorbent articles 80 include a liquid permeable top sheet or liner82, a back sheet or outercover 84 and an absorbent core 86 disposedbetween and contained by the top sheet 82 and back sheet 84. Articles 80such as diapers may also include some type of fastening means 88 such asadhesive fastening tapes or mechanical hook and loop type fasteners.

The multilayer film 10 by itself or in other forms such as themultilayer film/support layer laminate 32 may be used to form variousportions of the article including, but not limited to, the top sheet 82and the back sheet 84. If the film is to be used as the liner 82, itwill most likely have to be apertured or otherwise made to be liquidpermeable. When using a multilayer film/nonwoven laminate 32 as theoutercover 84, it is usually advantageous to place the nonwoven sidefacing out away from the user. In addition, in such embodiments it maybe possible to utilize the nonwoven portion of the laminate 32 as theloop portion of the hook and loop combination.

Other uses for the multilayer film and multilayer film/support layerlaminates according to the present invention include, but are notlimited to, surgical drapes and gowns, wipers, barrier materials andarticles of clothing or portions thereof including such items asworkwear and lab coats.

Test Methods

The properties of the present invention were determined using a seriesof test procedures which are set forth below. These properties includefilm thicknesses, water vapor transmission rates and peel strengths.

Water Vapor Transmission Rate

The water vapor transmission rate (WVTR) for the sample materials wascalculated in accordance with ASTM Standard E96-80. Circular samplesmeasuring three inches in diameter were cut from each of the testmaterials and a control which was a piece of CELGARD® 2500 film fromHoechst Celanese Corporation of Sommerville, N.J. CELGARD® 2500 film isa microporous polypropylene film. Three samples were prepared for eachmaterial. The test dish was a number 60-1 Vapometer pan distributed byThwing-Albert Instrument Company of Philadelphia, Pa. One hundredmilliliters of water was poured into each Vapometer pan and individualsamples of the test materials and control material were placed acrossthe open tops of the individual pans. Screw-on flanges were tightened toform a seal along the edges of each pan, leaving the associated testmaterial or control material exposed to the ambient atmosphere over a6.5 centimeter diameter circle having an exposed area of approximately33.17 square centimeters. The pans were placed in a forced air oven at100° F. (32° C.). The oven was a constant temperature oven with externalair circulating through it to prevent water vapor accumulation inside. Asuitable forced air oven is, for example, a Blue M Power-O-Matic 60 ovendistributed by Blue M Electric Company of Blue Island, Ill. After 24hours, the pans were removed from the oven and weighed again. Thepreliminary test water vapor transmission rate values were calculated asfollows:

Test WVTR=(grams weight loss over 24 hours)×315.5 g/m²/24 hrs

The relative humidity within the oven was not specifically controlled.

Under predetermined set conditions of 100° F. (32° C.) and ambientrelative humidity, the WVTR for the CELGARD® 2500 control has beendetermined to be 5000 grams per square meter for 24 hours. Accordingly,the control sample was run with each test and the preliminary testvalues were corrected to set conditions using the following equation:

WVTR=(Test WVTR/control WVTR)×5000 g/m²/24 hrs.) (g/m²/24 hrs)

Film/Film Layer Thicknesses

The overall thickness 28, first skin thickness 24, core thickness 22 andsecond skin thickness 26 were measured in cross-section by FieldEmission Scanning Electron Microscopy (FESEM). Each film sample wassubmersed in liquid nitrogen and cut on impact with a razor blade. Thefreshly cut cross-section was mounted to a specimen stub in an uprightposition using copper tape. The samples were observed using an HitachiS-800 Field Emission Scanning Electron Microscope at 5 and 10 keV.Scanning electron photomicrographs were taken at 2000×magnification toshow the film structures for each sample. Three separate samples andcorresponding pictures were prepared for each multilayer film. The 10.2centimeter by 12.7 centimeter negatives were enlarged to 20.4 centimeterby 25.4 centimeter copies and the measurements were taken directly offthese photographs. A reference 15 micron scale magnified at 2000× wassuperimposed on each photo. Five measurements for each of the layers wasmade on each of the three photos for each film sample thereby creating15 datapoints or measurements for each thickness. Measurements were madefor the first skin layer, the second skin layer and the core layer ofeach sample. The 15 measurements for each layer were combined andaveraged to yield a thickness value in microns for each layer. The totalthickness of the overall film was obtained by adding the average valuesfor the core layer, first skin layer and second skin layer for eachsample. The relative percentage of each skin layer was obtained bydividing the average thickness of the respective skin layer by theaverage overall thickness of the same sample and multiplying the resultby 100 to yield percent.

180° T Peel Test

To test the bond strength between the film layer and the fibrousnonwoven comfort layer, a delamination or peel strength test wasperformed upon samples of the various materials. 10.2 centimeter (cm) byapproximately 15.2 centimeter (cm) samples of the material were cut. Tothe film side of the samples there was applied a 10.2 cm by 15.2 cmpiece of 3M 2308 masking tape. The sample were then rolled, tape sideup, forward and backwards two times with a 22.2 kilogram roller weight.The samples were then manually delaminated at one of the short ends toproduce edges which could be placed within the jaws of a Sintech®/2Computer Integrated Testing System manufactured by MTS SystemsCorporation of Eden Prairie, Minn. The jaw gap was set at a span of 100millimeters and enough of the material was left in the laminated stateso that the jaws could travel 65 millimeters. The sample was positionedin the jaws so that the sample would start delaminating before the jawshad been expanded 10 millimeters. The crosshead speed was set at 300millimeters per minute and the data were then recorded between the 10millimeter start point and the 65 millimeter end point. The datarecorded indicated the peel strength or load necessary in grams toseparate the two layers and the standard index in grams with a maximum,minimum and mean value.

EXAMPLES

All the example films were three layer films with the two outer or skinlayers in each example being the same. All films were cast films and allthe films were embossed prior to stretching to yield a matte finish onthe films. In addition, all the films were laminated to a 17 gram persquare meter (gsm) polypropylene spunbond web made from approximately 2denier fibers. The spunbond web was prebonded with a point bond patternhaving an overall bond area of approximately 15 percent.

Example 1

In Example 1 the core layer was, on a weight percent basis based uponthe total weight of the layer, 65 percent ECC English China Supercoat™calcium carbonate with a 1 micron average particle size and a 7 microntop cut. The calcium carbonate was obtained from ECCA Calcium Products,Inc. of Sylacauga, Ala. which is a division of ECC International. Thecore layer also included 15 percent Exxon 9302 Random CopolymerPolypropylene (RCP) from the Exxon Chemical Company of Houston, Tex., 15percent Himont KS059 Catalloy polymer from Himont U.S.A. of Wilmington,Del. and 5 percent Quantum NA206 Low Density Polyethylene (LDPE) fromQuantum Chemical Corporation of New York, N.Y. The Himont Catalloypolymer is an olefinic thermoplastic elastomer or TPO multistep reactorproduct wherein an amorphous ethylene propylene random copolymer ismolecularly dispersed in a predominately semicrystalline highpolypropylene monomer/low ethylene monomer continuous matrix.

The two outer or skin layers on opposite sides of the core layercomprised 15 percent Himont KS057 Catalloy polymer from Himont U.S.A.,20 percent Ampacet 10115 antiblock and 65 percent Exxon XC-101 (28percent EMA copolymer). Ampacet 10115 antiblock comprises 20 weightpercent Superfloss™ diatomaceous earth let down in 79.75 percent Chevron2207 EMA and 0.25 percent aluminum stearate. Ampacet 10115 antiblock isavailable from Ampacet Corporation of Tarrytown, N.Y. Chevron 2207 EMAis available from the Chevron Chemical Corporation of San Ramon, Calif.and Exxon XC-101 is available from the Exxon Chemical Company ofHouston, Tex.

The three layer film was extruded using cast extrusion equipment of thetype described above. The exiting melt temperature for the skin layerswas measured to be 196° C. and for the core was 223° C. The air gap(distance between the die and the nip chill roll) was 53 centimeters andthe gauge of the resultant film was 38 micrometers (microns). The filmwas wound up on a roll and later sent through a Machine DirectionOrienter (MDO) Model No. 7200 from the Marshall and Williams Company ofProvidence, Rhode Island. The MDO unit was preheated to 77° C. and thefilm was stretched 4× while at a temperature of 77° C. By saying thefilm was stretched 4× it is meant that, for example, a 1 meter long filmwould be stretched to a resultant length of 4 meters. The final measuredthickness of the film was 16.08 microns and the basis weight was 17grams per square meter (gsm). Each of the two skin layers comprisedapproximately 2.7 percent of the overall film thickness. As a result,the core layer represented 94.6 percent of the overall thickness. Usingthe film thickness measuring method described above, the two skin layerseach had a film thickness of 0.44 microns and the core layer had athickness of 15.2 microns.

The resultant film was then thermally laminated to the above-describedspunbond layer using a patterned bonding roll having a temperature ofapproximately 77° C. and a smooth anvil roll at a temperature ofapproximately 54° C. with a nip pressure of 4,218 kilograms per meter(kg/m) while at a line speed of 152 meters per minute with and overallbond area of 15 percent based upon the surface area of one side of thefilm. The laminate was passed through the bonder in such a fashion thatthe spunbond layer was adjacent the pattern roll and the film layer wasadjacent the smooth anvil roll. The resultant laminate had a Water VaporTransmission Rate (WVTR) measured as described above of 2570 grams persquare meter per 24 hours (2570 g/m²/24 hr or day). The laminate had ahydrohead of 70 centimeters and a peel strength of 48 grams.

Example 2

In Example 2 the core layer was, on a weight percent basis based uponthe total weight of the layer, 65 percent ECC English China Supercoat™calcium carbonate, 15 percent Exxon 9302 Random Copolymer Polypropylene(RCP), 15 percent Himont KS059 Catalloy polymer and 5 percent QuantumNA206 Low Density Polyethylene (LDPE).

The two outer or skin layers on opposite sides of the core layercomprised 15 percent Ampacet 10115 antiblock (20 percent diatomaceousearth antiblock let down in a 24 percent copolymer ethylene methylacrylate (EMA)) concentrate or masterbatch and 85 percent Himont KS057Catalloy polymer.

The three layer film was extruded using cast extrusion equipment of thetype described above. The exiting melt temperature from the extruder forthe skin layers was 188° C. and the melt temperature for the core layerwas 223° C. The air gap (distance between the die heads and the formingnip) was 53 centimeters and the gauge of the resultant film was 35.5microns. The film was wound up on a roll and later sent through the MDOunit which was preheated to 88° C. and the film was stretched 3× whileat a temperature of 88° C. The final measured thickness of the film was17.28 microns and the basis weight was 15 gsm. Each of the two skinlayers comprised 2 percent of the overall film thickness. As a result,the core layer represented 96 percent of the overall thickness. Usingthe film thickness measuring method described above, the two skin layerseach had a film thickness of 0.33 micrometers (microns) and the corelayer had a thickness of 16.62 microns.

The resultant film was then thermally laminated to the above-describedspunbond layer using a patterned bonding roll having a temperature ofapproximately 77° C. and a smooth anvil roll at a temperature ofapproximately 54° C. with a nip pressure of 4,218 kg/m while at a linespeed of 152 meters per minute with and overall bond area of 15 to 18percent based upon the surface area of one side of the film. Thelaminate was passed through the bonder in such a fashion that thespunbond layer was adjacent the pattern roll and the film layer wasadjacent the anvil roll. The film had a Water Vapor Transmission Rate(WVTR) measured as described above of 925 grams per square meter per 24hours and the laminate had a WVTR of 820 g/m²/24 hr. The laminate had ahydrohead of 113 centimeters and a peel strength of 62 grams.

Example 3

In example 3 the core layer was, on a weight percent basis based uponthe total weight of the layer, 63 percent ECC English China Supercoat™calcium carbonate, 19 percent Himont KS059 Catalloy polymer, 13 percentShell 6D81 polypropylene from the Shell Chemical Company of Houston,Tex. and 5 percent Dow 4012 low density polyethylene (LDPE) from DowChemical U.S.A. of Midland, Mich. The two outer or skin layers onopposite sides of the core layer comprised 30 percent Himont KS057Catalloy polymer, 20 percent Techmer S110128E62 antiblock/EVAconcentrate or masterbatch from Techmer PM of Rancho Dominguez, Calif.,20 percent Exxon 760.36 EMA and 30 percent Lotryl 29MA03 Ester-ModifiedEMA copolymer from Elf Atochem N.A. of Philadelphia, Pa.

The three layer film was extruded using cast extrusion equipment. Theexiting temperature from the extruder for the skin layers was 188° C.and for the core was 209° C. The air gap (distance between the die headsand the forming roll) was 66 centimeters and the gauge of the resultantfilm was 38 microns. The film was wound up on a roll and later sentthrough the MDO unit which was preheated to 71° C. and the film wasstretched 4× while at a temperature of 71° C. and subsequently annealedat a temperature of approximately 85° C.

The final gauge of the film was 16.98 microns and the basis weight was17 gsm. Each of the two skin layers comprised 3.7 percent of the overallfilm thickness. As a result, the core layer represented 92.6 percent ofthe overall thickness. Using the film thickness measuring methoddescribed above, the two skin layers each had a film thickness of 0.6microns and the core layer had a thickness of 15.77 microns.

The resultant film was then thermally laminated to the above-describedspunbond layer using a patterned bonding roll having a temperature ofapproximately 110° C. and a smooth anvil roll at a temperature ofapproximately 32° C. with a nip pressure of 4570 kg/m inch while at aline speed of 61 meters per minute with and overall bond area of 15 to18 percent based upon the per unit surface area of one side of the film.The laminate was passed through the bonder in such a fashion that thespunbond layer was adjacent the pattern roll and the film layer wasadjacent the anvil roll. The film had a Water Vapor Transmission Rate(WVTR) measured as described above of 1301 grams per square meter per 24hours (1301 g/m²/24 hr) and the resultant laminate had a WVTR of 1184g/m²/24 hr. The laminate had a hydrohead of 110 centimeters and a peelstrength of 161 grams.

Example 4

In Example 4 the core layer was, on a weight percent basis based uponthe total weight of the layer, 63 percent ECC English China Supercoat™calcium carbonate, 19 percent Himont KS059 Catalloy polymer, 13 percentShell 6D81 polypropylene and 5 percent Dow 4012 LDPE.

The two outer or skin layers on opposite sides of the core layercomprised 35 percent Himont KS057 Catalloy polymer, 20 percent TechmerS110128E62 antiblock/EVA concentrate/masterbatch and 45 percent Exxon760.36 EMA.

The three layer film was extruded using cast extrusion equipment. Theexiting temperature for the skin layers was 187° C. and for the core was208° C. The air gap (distance between the die heads and the formingroll) was 66 centimeters and the gauge of the resultant film was 35.5microns. The film was wound up on a roll and later sent through the MDOunit which was preheated to 71° C. and the film was stretched 4× whileat a temperature of 71° C. and subsequently annealed at a temperature ofapproximately 85° C. The final measured thickness of the film was 15.96microns and the basis weight was 15 gsm. Each of the two skin layerscomprised 3.0 percent of the overall film thickness. As a result, thecore layer represented 94.0 percent of the overall thickness. Using thefilm thickness measuring method described above, the two skin layerseach had a film thickness of 0.48 microns and the core layer had athickness of 15.0 microns.

The resultant film was then thermally laminated to the above-describedspunbond layer using a patterned bonding roll having a temperature ofapproximately 110° C. and a smooth anvil roll at a temperature ofapproximately 66° C. with a nip pressure of 4570 kg/m while at a linespeed of 61 meters per minute with and overall bond area of 15 to 18percent based upon the per unit surface area of one side of the film.The laminate was passed through the bonder in such a fashion that thespunbond layer was adjacent the pattern roll and the film layer wasadjacent the anvil roll. The resultant laminate had a WVTR of 1522g/m²/24 hrs., a hydrohead of 89 centimeters and a peel strength of 148grams.

Example 5

In Example 5 the core layer was, on a weight percent basis based uponthe total weight of the layer, 65 percent ECC English China Supercoat™calcium carbonate, 15 percent Himont KS059 Catalloy polymer, 15 percentExxon 9302 Random Copolymer Polypropylene (RCP) and 5 percent Dow 4012LDPE.

The two outer or skin layers on opposite sides of the core layercomprised 35 percent Himont KS057 Catalloy polymer, 20 percent TechmerS110128E62 antiblock/EVA concentrate/masterbatch and 45 percent Exxon760.36 EMA.

The three layer film was extruded using cast extrusion equipment. Theexiting temperature for the skin layers was 175° C. and for the core was234° C. The air gap (distance between the die heads and the formingroll) was 33 centimeters and the gauge of the resultant film was 35.5microns. The film was wound up on a roll and later sent through the MDOunit which was preheated to 77° C. and the film was stretched 4× whileat a temperature of 77° C. and subsequently annealed at a temperature ofapproximately 75° C. The final measured thickness of the film was 16.92microns and the basis weight was 15 gsm. Each of the two skin layerscomprised 1.0 percent of the overall film thickness. As a result, thecore layer represented 98.0 percent of the overall thickness. Using thefilm thickness measuring method described above, the two skin layerseach had a film thickness of 1.75 microns and the core layer had athickness of 16.57 microns.

The resultant film was then thermally laminated to the above-describedspunbond layer using a patterned bonding roll having a temperature ofapproximately 73° C. and a smooth anvil roll at a temperature ofapproximately 51° C. with a nip pressure of 4218 kg/m while at a linespeed of 152 meters per minute with and overall bond area of 15 to 18percent based upon the per unit surface area of one side of the film.The laminate was passed through the bonder in such a fashion that thespunbond layer was adjacent the pattern roll and the film layer wasadjacent the anvil roll. The resultant laminate had a WVTR of 1930g/m²/24 hrs., a hydrohead of 66 centimeters and a peel strength of 116grams.

As shown by the above examples of the present invention, very lowthickness (less than 30 microns) multilayer films can be formed. Inaddition, such films can have very thin skin layers which can impart awide variety of functionalities including making the film vaporpermeable, liquid impermeable and adhesive in nature. Furthermore suchfilms can be attached to other support layers such as nonwoven to formlaminates.

Having thus described the invention in detail, it should be apparentthat various modifications can be made in the present invention withoutdeparting from the spirit and scope of the following claims.

What is claimed is:
 1. A multilayer film, comprising: a liquidimpermeable multilayer film having a thickness less than 30 microns anda WVTR of at least 300 g/m²/24 hours, said multilayer film comprising acore layer and first and second skin layers; said core layer comprisingan extrudable thermoplastic polymer and a particulate filler whereinpores are located adjacent said filler; said first skin layer on a firstside of the core layer, and having a thickness constituting less thanabout 7.5% of the thickness of the multilayer film; and said second skinlayer on a second side of the core layer and having a thicknessconstituting less than about 7.5% of the thickness of the multilayerfilm; each of said first and second skin layers comprise a polymerselected from the group consisting of polyolefins, ethylene vinylacetate, ethylene ethyl acrylate, ethylene acrylic acid, ethylene methylacrylate, ethylene butyl acrylate, polyester, nylon, ethylene vinylalcohol, polystyrene, polyurethane, olefinic thermoplastic elastomers ofethylene and propylene, and combinations thereof.
 2. The multilayer filmof claim 1, wherein at least one of the first and second skin layerscomprises a polymer selected from the group consisting of polyolefins,ethylene vinyl acetate, polystyrene, olefinic thermoplastic elastomersof ethylene and propylene, and combinations thereof.
 3. The multilayerfilm of claim 1, wherein each of the first and second skin layerscomprises a polymer selected from the group consisting of polyolefins,ethylene vinyl acetate, polystyrene, olefinic thermoplastic elastomersof ethylene and propylene, and combinations thereof.
 4. The multilayerfilm of claim 1, wherein at least one of the first and second skinlayers comprises a polyolefin and an olefinic thermoplastic elastomer,said elastomer being a multistep reactor product wherein an amorphousethylene-propylene random copolymer is molecularly dispersed in acontinuous matrix of a predominantly semi-crystalline copolymer ofpropylene monomer/ethylene monomer.
 5. The multilayer film of claim 1,wherein both of the skin layers comprise a polyolefin and an olefinicthermoplastic elastomer, said elastomer being a multistep reactorproduct wherein an amorphous ethylene-propylene random copolymer ismolecularly dispersed in a continuous matrix of a predominantlysemi-crystalline copolymer of propylene monomer/ethylene monomer.
 6. Themultilayer film of claim 1, wherein at least one of the first and secondskin layers comprises an ethylene vinyl acetate and an olefinicthermoplastic elastomer, the elastomer being a multistep reactor productwherein an amorphous ethylene-propylene random copolymer is molecularlydispersed in a continuous matrix of a predominately semi-crystallinecopolymer of propylene monomer/ethylene monomer.
 7. The multilayer filmof claim 1, wherein both of the skin layers comprise an ethylene vinylacetate and an olefinic thermoplastic elastomer, the elastomer being amultistep reactor product wherein an amorphous ethylene-propylene randomcopolymer is molecularly dispersed in a continuous matrix of apredominately semi-crystalline copolymer of propylene monomer/ethylenemonomer.
 8. The multilayer film of claim 1, wherein at least one of thefirst and second skin layers comprises a polyolefin and an ethylenevinyl acetate.
 9. The multilayer film of claim 1, wherein both of theskin layers comprise a polyolefin and an ethylene vinyl acetate.
 10. Themultilayer film of claim 1, wherein at least one of the first and secondskin layers comprises a polyolefin and a polystyrene.
 11. The multilayerfilm of claim 1, wherein both of the skin layers comprise a polyolefinand a polystyrene.
 12. The multilayer film of claim 1, wherein at leastone of the first and second skin layers comprises an ethylene vinylacetate and a polystyrene.
 13. The multilayer film of claim 1, whereinboth skin layers comprise an ethylene vinyl acetate and a polystyrene.14. The multilayer film of claim 3 wherein said core layer comprises apolyethylene and wherein each of the skin layers has a thickness lessthan 2 microns.
 15. The multilayer film of claim 14, wherein the corelayer comprises at least about 60% by weight particulate filler.
 16. Themultilayer film of a claim 1 wherein said extrudable thermoplasticpolymer of said core layer comprises an olefin polymer and furtherwherein said thermoplastic polymer of the first skin layer comprises apolyolefin and an ethylene copolymer selected from the group consistingof ethylene vinyl acetate, ethylene ethyl acrylate and ethylene methylacrylate.
 17. The multilayer film of claim 16 wherein said thermoplasticpolymer of the second skin layer comprises a polyethylene and anethylene copolymer selected from the group consisting of ethylene vinylacetate, ethylene ethyl acrylate and ethylene methyl acrylate.
 18. Themultilayer film of claim 17 wherein each of said first and second skinlayers has a film thickness less than 2 micrometers.
 19. The multilayerfilm of claim 18 wherein the extrudable thermoplastic polymer of saidcore layer comprises a polyethylene.
 20. The multilayer film of claim 19wherein the core layer comprises at least about 60% by weightparticulate filler.
 21. The multilayer film of claim 1 wherein saidthermoplastic polymer of the first skin layer comprises a polyethyleneand an ethylene copolymer selected from the group consisting of ethylenevinyl acetate, ethylene ethyl acrylate, ethylene methyl acrylate,ethylene butyl acrylate, ethylene acrylic acid and ethylene vinylalcohol.
 22. The multilayer film of claim 21 wherein said thermoplasticpolymer of the second skin layer comprises a polyethylene and anethylene copolymer selected from the group consisting of ethylene vinylacetate, ethylene ethyl acrylate, ethylene methyl acrylate, ethylenebutyl acrylate, ethylene acrylic acid and ethylene vinyl alcohol. 23.The multilayer film of claim 22 wherein each of said first and secondskin layers has a film thickness less than 2 micrometers.
 24. Themultilayer film of claim 23 wherein said extrudable thermoplasticpolymer of said core layer comprises a polyethylene.
 25. The multilayerfilm of claim 24 wherein the filler comprises at least about 60% byweight of the core layer.
 26. A breathable laminate, comprising themultilayer film of claim 1 and a nonwoven fabric attached to said firstskin layer.
 27. The breathable laminate of claim 26 wherein saidnonwoven fabric comprises a nonwoven fabric of polyolefin fibers. 28.The breathable laminate of claim 26 wherein said nonwoven fabric isthermally laminated to said multilayer film at a plurality of bondpoints.
 29. A breathable laminate, comprising the multilayer film ofclaim 1 and a first nonwoven fabric attached to said first skin layerand a second support fabric attached to said second skin layer.
 30. Abreathable laminate, comprising the multilayer film of claim 17 and anonwoven fabric attached to said first skin layer.
 31. A multilayer,stretch-thinned breathable film having an overall thickness notexceeding about 30 microns and a moisture vapor transmission rate inexcess of 300 grams/m²/24 hours, comprising: a core layer including amixture of an extrudable thermoplastic polymer and a particulate filler;and a skin layer on a side of the core layer, having a skin layerthickness; the skin layer thickness constituting less than about 10% ofthe overall thickness; the skin layer comprising a polymer selected fromthe group consisting of polyolefins, ethylene vinyl acetate, ethyleneethyl acrylate, ethylene acrylic acid, ethylene methyl acrylate,ethylene butyl acrylate, polyester, nylon, ethylene vinyl alcohol,polystyrene, polyurethane, olefinic thermoplastic polymers of ethyleneand propylene, and combinations thereof.
 32. The multilayer film ofclaim 31, wherein the skin layer comprises a polymer selected from thegroup consisting of polyolefins, ethylene vinyl acetate, polystyrene,olefinic thermoplastic polymers of ethylene and propylene, andcombinations thereof.
 33. The multilayer film of claim 31, wherein theskin layer comprises a polyolefin and an olefinic thermoplasticelastomer, the elastomer being a multistep reactor product wherein anamorphous ethylene-propylene random copolymer is molecularly dispersedin a continuous matrix of a predominately semi-crystalline copolymer ofpropylene monomer/ethylene monomer.
 34. The multilayer film of claim 33,wherein the skin layer comprises an ethylene vinyl acetate and anolefinic thermoplastic elastomer, the elastomer being a multistepreactor product wherein an amorphous ethylene-propylene random copolymeris molecularly dispersed in a continuous matrix of a predominatelysemi-crystalline copolymer of propylene monomer/ethylene monomer. 35.The multilayer film of claim 31, wherein the skin layer comprises apolyolefin and an ethylene vinyl acetate.
 36. The multilayer film ofclaim 31, wherein the skin layer comprises a polyolefin and apolystyrene.
 37. The multilayer film of claim 31, wherein the skin layercomprises an ethylene vinyl acetate and a polystyrene.
 38. Themultilayer film of claim 31, wherein the core layer comprises at leastabout 60% by weight particulate filler.
 39. A personal care absorbentarticle including a liquid permeable top sheet, a breathable back sheetand an absorbent core between the top sheet and the back sheet, the backsheet including the multilayer film of claim
 1. 40. A personal careabsorbent article including a liquid permeable top sheet, a breathableback sheet and an absorbent core between the top sheet and the backsheet, the back sheet including the multilayer film of claim
 3. 41. Apersonal care absorbent article including a liquid permeable top sheet,a breathable back sheet and an absorbent core between the top sheet andthe back sheet, the back sheet including the multilayer film of claim17.
 42. A personal care absorbent article including a liquid permeabletop sheet, a breathable back sheet and an absorbent core between the topsheet and the back sheet, the back sheet including the breathablelaminate of claim
 26. 43. A personal care absorbent article including aliquid permeable top sheet, a breathable back sheet and an absorbentcore between the top sheet and the back sheet, the back sheet includingthe breathable laminate of claim
 29. 44. A personal care absorbentarticle including a liquid permeable top sheet, a breathable back sheetand an absorbent core between the top sheet and the back sheet, the backsheet including the multilayer film of claim 30.